The present invention generally relates to laser construction and, more particularly, to a bore support assembly for supporting a bore tube in a laser and to a method of constructing a laser by joining two or more outer envelop sections utilizing one or more of the bore support assemblies.
Gas discharge lasers, such as helium-neon gas lasers, use a bore tube for confining the discharge to maximize the power output. In the coaxial design of such lasers, an outer envelop defines a cavity, an anode and cathode are located within the cavity at opposite ends of the outer envelop, end mirrors are mounted on the ends of the envelop, and the bore tube is mounted within the envelop in alignment with the end mirrors. One end of the bore tube is connected to one end of the outer envelop so as to be fixed in position. The other end of the bore tube is free and projects within the cavity toward the opposite end of the envelop.
The bore tube is heated by operation of the laser to a substantially higher temperature than the temperature reached by the outer envelop. Since the bore tube is subjected to a higher temperature than the outer envelop as the laser is energized from a non-operating condition to an operating condition, the length of the bore tube increases at a slightly greater rate than the length of the outer envelop. The free end of the bore tube must therefore be permitted to shift longitudinally with respect to the outer envelop to accommodate this slight difference in thermal expansion.
While longitudinal, or axial, expansion of the bore tube must be permitted, shifting of the bore tube free end transverse to the laser axis must be restrained to prevent loss of laser power. In one arrangement disclosed in U.S. Pat. No. 4,644,554, issued Feb. 17, 1987 to Sheng, and assigned to the assignee of the present invention, the free end of the bore tube is supported in the laser outer envelop by a spider structure. The spider structure is constructed to be substantially rigid against transverse movement of the free end of the bore tube while permitting sufficient longitudinal movement of the bore tube free end to accommodate the differential thermal expansion of the bore tube with respect to the envelop which occurs during laser operation.
The above-described arrangement for supporting the bore tube has been highly successful in construction of shorter, lower power gas discharge lasers. However, this arrangement cannot be directly scaled up for use in the construction of longer, higher power gas discharge lasers. Thus, a need exists for a fresh approach to construction of higher power gas discharge lasers so as to overcome the construction difficulties which were previously experienced.